A catalyst for olefin polymerization is provided which comprises, as the components, a) a metallocene compound, b) an ionizing ionic compound, c) an organoaluminum compound, and d) a Lewis base compound. This catalyst has a stable active species and improves productivity of an olefin polymer without...http://www.google.com.au/patents/US5576259?utm_source=gb-gplus-sharePatent US5576259 - Process for producing α-olefin polymer

A catalyst for olefin polymerization is provided which comprises, as the components, a) a metallocene compound, b) an ionizing ionic compound, c) an organoaluminum compound, and d) a Lewis base compound. This catalyst has a stable active species and improves productivity of an olefin polymer without deterioration of the catalytic activity.

a) the metallocene compound being represented by General Formula (1) or (2): ##STR3## where Cp1, Cp2, Cp3 and Cp4 are independently a substituted or unsubstituted cyclopentadienyl, indenyl, or fluorenyl group; R1 is a substituted or unsubstituted alkylene, dialkylsilanediyl, dialkylgermanediyl, alkylphosphinediyl, or alkylimino group, and R1 links Cp1 with Cp2 by bridging; M is a titanium atom, a zirconium atom, or a hafnium atom; and R2, R3, R4 and R5 are independently a hydrogen atom, a halogen atom, a hydrocarbon group of 1 to 12 carbon atoms, an alkoxy group, or aryloxy group;

b) the ionizing ionic compound being a compound which is capable of changing the above a) metallocene compound into a cationic metallocene compound;

c) the organoaluminum compound being represented by General Formula (3): ##STR4## where R6, R6', and R6" are independently a hydrogen atom a halogen atom, an amino group, an alkyl group, an alkoxy group, or an aryl group, and at least one of R6, R6', and R6" is an alkyl group;

d) the Lewis base compound being capable of donating an electron to the formed cationic metallocene compound, said Lewis base compound being present in an amount between 10 and 1,000 moles per mole of the metallocene compound.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a catalyst for producing an α-olefin comprising a metallocene, an organoaluminum compound, an ionizing ionic compound, and a Lewis base compound. The present invention also relates to a process for producing an α-olefin polymer employing the above catalyst.

2. Description of the Relate Art

For polymerization of olefins, special active catalysts are known which comprise combination of a cyclopentadienyl derivative of a metal such as titanium, zirconium, and hafnium (Group 4B of Periodic Table) with aluminoxane.

This type of catalyst is not used practically in commercial production of olefin polymers mainly because of the following disadvantages: the aluminoxane cannot readily be synthesized with high reproducibility, and therefore preparation of the catalyst and production of the polymers cannot be conducted with sufficient reproducibility; and aluminoxane is required to be used in a high ratio to the transition metal compound to achieve sufficient catalyst activity although the raw material of aluminoxane, e.g., trimethylaluminum, is expensive.

To offset the disadvantages, ionic metallocene catalysts are reported. JP-A-3-207704 discloses an ionic metallocene compound prepared by reacting a metallocene compound with an ionizing ionic compound. WO92/01723 discloses an α-olefin polymerization process employing a catalyst system prepared by reacting a halogenated metallocene compound with an organometallic compound and further bringing the product into contact with an ionizing ionic compound, the catalyst system having sufficient catalytic activity.

The catalyst system employing an ionizing ionic compound, which has a high initial activity, loses its activity with progress of polymerization, disadvantageously.

After comprehensive study to solve the above problems, the inventors of the present invention have found that a catalyst prepared by reacting an ionic metallocene catalyst with a Lewis base compound has a stable catalytic species, and exhibits improved productivity of polymers without deterioration of the catalytic activity.

SUMMARY OF THE INVENTION

The present invention intends to improve productivity of polymers by stabilizing the active species of the catalyst to prevent deterioration of the catalyst activity without the above disadvantages of the prior art.

The present invention provides a catalyst for polymerization of olefin, comprising a) a metallocene compound, b) an ionizing ionic compound, c) an organoaluminum compound, and d) a Lewis base compound:

a) the metallocene compound being represented by General Formula (1) or (2): ##STR1## where Cp1, Cp2, Cp3 and Cp4 are independently a substituted or unsubstituted cyclopentadienyl, indenyl, or fluorenyl group; R1 is a substituted or unsubstituted alkylene, dialkylsilanediyl, dialkylgermanediyl, alkylphosphinediyl, or alkylimino group, and R1 links Cp1 with Cp2 by bridging; M is a titanium atom, a zirconium atom, or a hafnium atom; and R2, R3, R4 and R5 are independently a hydrogen atom, a halogen atom, a hydrocarbon group of 1 to 12 carbon atoms, an alkoxy group of 1 to 12 carbon atoms, or aryloxy group;

b) the ionizing ionic compound being a compound which is capable of changing the above metallocene compound (a) into a cationic metallocene compound and does not react further the formed cationic metallocene compound;

c) the organoaluminum compound being represented by General Formula (3): ##STR2## where R6, R6', and R6" are independently a hydrogen atom, a halogen atom, an amino group, an alkyl group, an alkoxy group, or an aryl group, and at least one of R6, R6', and R6" is an alkyl group;

d) the Lewis base compound being capable of donating an electron to the formed cationic metallocene compound.

The present invention also provides a process for producing an α-olefin polymer by polymerizing α-olefin in the presence of the above catalyst.

DETAILED DESCRIPTION OF THE INVENTION

The metallocene compound (a) employed in the present invention is represented by General Formula (1) or (2). The specific examples thereof include:

thioacetals such as 1-ethoxy-1-(methylthio)cyclopentane, thioketones such as cyclohexanethione;

and the like, but the Lewis base compound is not limited thereto.

The α-olefin in the present invention includes specifically ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, and styrene, but is not limited thereto, and two or more thereof may be used in combination.

The catalyst may be prepared in the present invention by mixing the aforementioned components of a metallocene compound (a), an ionizing ionic compound (b), an organoaluminum compound (c) and a Lewis base compound (d), for example, in an inert solvent. The method of catalyst preparation is not limited thereto.

The ionizing ionic compound (b) is used in an amount of preferably not less than one mole per mole of the metallocene compound (a) in the present invention to obtain a desirable catalyst activity. Although the upper limit is not specified, the amount of the ionizing ionic compound to be used is preferably not more than 100 moles per mole of the metallocene compound in consideration of the ash content of the produced polymer, or not more than 30 moles per mole of the metallocene compound in consideration of the cost.

The organic aluminum compound (c) is used in an amount of preferably not less than 10 moles per mole of the metallocene compound (a) in terms of aluminum to obtain a desirable catalyst activity, and not more than 100000 moles to suppress the chain transfer causing lowering of molecular weight and not to increase the ash content, although the amount is not limited thereto.

The Lewis base compound (d) is used in an amount of preferably not less than 0.1 mole per mole of the metallocene compound (a) to stabilize the active species and to prevent loss of the catalyst activity and raise polymer productivity, and preferably not more than 1000 moles not to retard the polymerization reaction.

The process for the polymerization is not specially limited, and includes slurry processes, gas phase processes, bulk processes, solution processes, and high-temperature high-pressure processes. The temperature of the polymerization is not specially limited, but is preferably not lower than 0° C. to obtain high productivity, and not higher than 300° C. to suppress the chain transfer causing lowering of molecular weight and maintain the catalyst efficiency. The pressure of the polymerization is not specially limited, but is preferably atmospheric pressure or higher to obtain high productivity.

The present invention is described more specifically by reference to examples without limiting the invention thereto.

The procedures of polymerization, reaction, and solvent purification were conducted in an inert atmosphere. The solvent used in the reaction was purified, dried, and/or deoxygenated by conventional methods. The compounds used in the reactions were synthesized and identified by conventional methods.

EXAMPLE 1

In a 1-liter reactor, was placed 600 ml of an aliphatic hydrocarbon (IP Solvent 1620, produced by Idemitsu Petrochemical Co.). The temperature of the reactor was maintained at 150° C. Ethylene was fed to the reactor at a pressure of 20 kg/cm2. Separately, a solution of 0.25 μmol of diphenylmethylene(cyclopentadienyl)(fluorenyl)zirconium dichloride in toluene was placed in another vessel, and thereto a solution of triisobutylaluminum in toluene (triisobutyl-aluminum: 20% by weight) was added in an amount of 62.5 μmol in terms of aluminum. The mixture was stirred for one hour. Then the mixture was added to a solution of 0.5 μmol of N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate in toluene, and the mixture was stirred for 10 minutes. To this mixture, a solution of 2.5 μmol of diisobutyl phthalate in toluene was added, and the mixture was stirred for 10 minutes. The resulting mixture was introduced into the aforementioned reactor by nitrogen pressure. The reactor was maintained at 150° C. with stirring at a rate of 1500 rpm for one hour. The resulting reaction product was dried at 100° C. under vacuum for 6 hours to obtain an ethylene polymer. The result is shown in Table 1.

EXAMPLE 2

An ethylene polymer was obtained in the same manner as in Example 1 except that 12.5 μmol of diphenyldimethoxysilane was used in place of 2.5 μmol of the diisobutyl phthalate. The result is shown in Table 1.

COMPARATIVE EXAMPLE 1

An ethylene polymer was obtained in the same manner as in Example 1 except that 2.5 μmol of diisobutyl phthalate was not used. The result is shown in Table 1.

EXAMPLE 3

In a 1-liter reactor, was placed 600 ml of an aliphatic hydrocarbon (IP Solvent 1620, produced by Idemitsu Petrochemical Co.). The temperature of the reactor was maintained at 150° C. Ethylene was fed to the reactor at a pressure of 20 kg/cm2. Separately, a solution of 1.0 μmol of ethylenebis(indenyl)zirconium dichloride in toluene was placed in another vessel, and thereto a solution of triisobutylaluminum (triisobutylaluminum: 20% by weight) was added in an amount of 250 μmol in terms of aluminum. The mixture was stirred for one hour. Then the mixture was added to a solution of 2 μmol of N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate in toluene, and the mixture was stirred for 10 minutes. To this mixture, a solution of 50 μmol of diisobutyl phthalate in toluene was added, and the mixture was stirred for 10 minutes. The resulting mixture was introduced into the aforementioned reactor by nitrogen pressure. The reactor was maintained at 150° C. with stirring at a rate of 1500 rpm for one hour. The resulting reaction product was dried at 100° C. under vacuum for 6 hours to obtain an ethylene polymer. The result is shown in Table 1.

EXAMPLE 4

An ethylene polymer was obtained in the same manner as in Example 3 except that 10 μmol of diphenyldimethoxysilane was used in place of 50 μmol of the diisobutyl phthalate. The result is shown in Table 1.

EXAMPLE 5

An ethylene polymer was obtained in the same manner as in Example 3 except that 50 μmol of diphenyldimethoxysilane was used in place of 50 μmol of the diisobutyl phthalate. The result is shown in Table 1.

EXAMPLE 6

An ethylene polymer was obtained in the same manner as in Example 3 except that 250 μmol of diphenyldimethoxysilane was used in place of 50 μmol of the diisobutyl phthalate. The result is shown in Table 1.

COMPARATIVE EXAMPLE 2

An ethylene polymer was obtained in the same manner as in Example 3 except that 50 μmol of diisobutyl phthalate was not used. The result is shown in Table 1.

The ionic metallocene catalyst of the present invention, as described above exhibits excellent catalytic activity in polymerization of α-olefin, and enables production of α-olefin polymer with high efficiency.